Stephen Jenco, senior research analyst at Grubb & Ellis, another national commercial brokerage, is not so sure.

HE said the model for such an effort was the firm of Coldwell Banker, which added residential brokerage to its existing commercial brokerage in 1937.

Cushman & Wakefield, the region's largest commercial brokerage, said asking prices had declined 10 percent since 1988.

The sale did not include Douglas Elliman's commercial brokerage and insurance operations, a spokesman for the Milstein family said.

And it also has a thriving commercial brokerage and consulting business, areas that Insignia has barely touched.

The guidelines, which were put together with the help of research directors from several commercial brokerages, will be offered in a manual describing procedural standards.

But that's no guarantee of future success, noted John Goodkind, an executive managing director with Newmark & Company, a commercial brokerage.

"We represent more than 350 enterprises, organizations and commercial, state, private brokerage and other enterprises," he said.

Cushman & Wakefield and Insignia, the two largest commercial brokerages in the city, have divergent views on the value of collecting data internally.

The county had a vacancy rate of 18 percent, up from 16.5 percent in 1997, according to Insignia/ESG, a commercial brokerage.